Safety Manual > Excavations, Trenching, and Shoring

I. EXCAVATIONS, TRENCHING, AND SHORING

1. All surface encumbrances that are located so as to create a hazard to employees
shall be removed or supported, as necessary, to safeguard employees.

2. The estimated location of utility installations, such as sewer, telephone, fuel,
electric, water lines, or any other underground installations that reasonably may
be expected to be encountered during excavation work, shall be determined before opening
an excavation by contacting local utility companies and Facility Services, to establish
the location of the utility underground installations.

3. An excavation permit shall be obtained from Facility Services prior to beginning
the excavation on campus.

4. When excavation operations approach the estimated location of underground installations,
the exact location of the installations shall be determined by safe and acceptable
means, such as probing and hand digging.

5. While the excavation is open, underground installations shall be protected, supported
or removed as necessary to safeguard employees.

6. Structural ramps that are used solely by employees as a means of access or egress
from excavations shall be designed by a competent person. Structural ramps used for
equipment shall be designed by a competent person qualified in structural design,
and shall be constructed in accordance with the design.

7. Structural ramps used in lieu of steps shall be provided with cleats or other surface
treatments on the top surface to prevent slipping.

8. A stairway, ladder, ramp or other safe means of egress shall be located in trench
excavations that are 4 feet (1.22 m) or more in depth so as to require no more than
25 feet of lateral travel for employees.

9. Employees exposed to public vehicular traffic shall be provided with, and shall
wear, warning vests or other suitable garments marked with or made of reflectorized
or high-visibility material.

10. When mobile equipment is operated adjacent to an excavation, or when such equipment
is required to approach the edge of an excavation, and the operator does not have
a clear and direct view of the edge of the excavation, a warning system shall be utilized
such as barricades, hand or mechanical signals, or stop logs. If possible, the grade
should be away from the excavation.

11. Where employees enter excavations greater than 4 feet in depth , and where oxygen
deficiency (atmospheres containing less than 19.5 percent oxygen) or a hazardous atmosphere
exists or could reasonably be expected to exist, the atmospheres in the excavation
shall be tested before entry. A hazardous atmosphere is one with greater than 20%
LEL or airborne exposure above OSHA PELs

12. Adequate precautions shall be taken to prevent employee exposure to atmospheres
containing less than 19.5 percent oxygen and other hazardous atmospheres, such as
a concentration of a flammable gas in excess of 20 percent of the lower flammable
limit of the gas.

13. When controls are used that are intended to reduce the level of atmospheric contaminants
to acceptable levels, testing shall be conducted as often as necessary to ensure that
the atmosphere remains safe.

14. Emergency rescue equipment, such as breathing apparatus, a safety harness and
line, or a basket stretcher, shall be readily available where hazardous atmospheric
conditions exist or may reasonably be expected to develop during work in an excavation.
Such equipment shall be attended while the work is in progress.

15. Employees entering bell-bottom pier holes, or other similar deep and confined
footing excavations, shall wear a harness with a lifeline securely attached to it.
The lifeline shall be separate from any line used to handle materials, and shall be
individually attended at all times while the employee wearing the lifeline is in the
excavation.

16. Employees shall not work in excavations in which there is accumulated water, or
in excavations in which water is accumulating, unless adequate precautions have been
taken to protect employees against the hazards posed by water accumulation. The precautions
necessary to protect employees adequately vary with each situation, but could include
special support or shield systems to protect from cave-ins, water removal to control
the level of accumulating water, or use of a safety harness and lifeline. If water
is controlled or prevented from accumulating by the use of water removal equipment,
the water removal equipment and operations shall be monitored by a competent person
to ensure proper operation.

17. If excavation work interrupts the natural drainage of surface water (such as streams),
diversion ditches, dikes, or other suitable means shall be used to prevent surface
water from entering the excavation and to provide adequate drainage of the area adjacent
to the excavation. Excavations subject to runoff from heavy rains will require an
inspection by a competent person.

18. Where the stability of adjoining sidewalks, poles, buildings, walls, footings
or other structures is endangered by excavation operations, support systems such as
shoring, bracing, or underpinning shall be provided to ensure the stability of such
structures for the protection of employees. An engineer shall determine if the condition
is safe where building footings or foundations are concerned.

19. Adequate protection shall be provided to protect employees from loose soil that
could pose a hazard by falling or rolling from an excavation face or from the surface
above. Such protection shall consist of scaling to remove loose material; installation
of protective barricades at intervals as necessary on the face to stop and contain
falling material, and by placing and keeping such materials or equipment at least
2 feet from the edge of excavations and / or by the use of retaining devices that
are sufficient to prevent materials or equipment from falling or rolling into excavations.

20. Daily inspections of excavations, the adjacent areas, and protective systems shall
be made by a competent person for evidence of a situation that could result in possible
cave-ins, indications of failure of protective systems, hazardous atmospheres, or
other hazardous conditions. An inspection shall be conducted by the competent person
prior to the start of work and as needed throughout the shift. Inspections shall also
be made after every rainstorm or other hazard increasing occurrence. These inspections
are only required when employee exposure can be reasonably anticipated.

21. Where the competent person finds evidence of a situation that could result in
a possible cave-in, indications of failure of protective systems, hazardous atmospheres,
or other hazardous conditions, exposed employees shall be immediately removed from
the hazardous area until the necessary precautions have been taken to ensure their
safety.

22. Walkways shall be provided where employees or equipment are required or permitted
to cross over excavations. Guardrails shall be provided where walkways are 6 feet
or more above lower levels.

23. Adequate barrier physical protection shall be provided at all remotely located
excavations. All wells, pits, shafts, etc., shall be barricaded or covered.

24. Where excavations are less than 5 feet (1.52 m) in depth and examination of the
ground by a competent person provides no indication of a potential cave-in, there
are no additional steps necessary to prevent cave-ins.

25. Excavations shall be sloped at an angle not steeper than one and one-half horizontal
to one vertical (34 degrees measured from the horizontal), unless one of the other
options provided for in the OSHA standard is used under the direction of the competent
person or registered professional engineer, as applicable.

26. Support systems shall be installed and removed in a manner that protects employees
from cave-ins, structural collapses, or from being struck by members of the support
system. Removal shall begin at, and progress from, the bottom of the excavation. Members
shall be released slowly so as to note any indication of possible failure of the remaining
members of the structure or possible cave-in of the sides of the excavation. Backfilling
shall progress together with the removal of support systems from excavations.

27. No more than two feet may be excavated below the bottom of the support system,
and this may occur only when the competent person/engineer has evaluated the conditions
and given approval.

28. If design of the excavation is performed by a professional engineer, at least
one copy of the design shall be maintained at the jobsite during construction of the
protective system.